The present invention is generally directed to a bridge and more particularly, to an improved pre-stressed, concrete bridge using longitudinal load members of a single continuous beam including at least two types of concrete, one of which is ultra-high-performance concrete (UHPC) mix with a compressive strength exceeding 137.9 Mpa (20 ksi) and tensile strength exceeding 10.34 Mpa (1.5 ksi) in a region proximate to the support structure.
Engineers are consistently striving to build bridges that are stronger, lighter, and capable of spanning longer distances while having improved durability and lower costs. Increasing the distance that a bridge may span without supporting piers or increasing the distance between supporting piers is also very desirable. To accomplish the above goals, engineers over the years have moved from stone and wood bridges to iron and steel bridges, to reinforced concrete bridges and more recently to pre-stressed concrete bridges.
Pre-stressed concrete bridges using pre-stressed beams have been widely implemented in the bridge construction in the last couple of decades. Prestressed beams are favored over steel or reinforced concrete beams because of their high load carrying capacities and their high span-to-depth ratio. However, certain deficiencies have been recently reported in prestressed beams such as: (1) cracking near the ends of the beams at the anchorage zones, (2) web distress and shear cracking, and (3) spalling of concrete and other durability issues associated with the corrosion of the longitudinal and transverse steel reinforcement. FIG. 1 shows an exemplary prestressed beam including a steel reinforcement shear plate.
In addition, unlike steel or reinforced concrete beams, continuity of prestressed beams is relatively hard to accomplish. Usually, prestressed beams are designed as simply supported for dead loads and continuous for life loads. The continuity for the life loads are typically achieved by providing a continuous cast-in-place deck slab. Nevertheless, the addition of cast-in-place deck slabs prolongs the on-site construction time and encounters further traffic interruption. In addition, the cast-in-place deck slab hinders the wide implementation of accelerated bridge construction (ABC) technique, which is developed primarily to expedite the bridge construction process, reduce the on-site construction work, and improve the quality and lifespan of the constructed bridges. ABC technique involves constructing precast concrete units off-site then transporting them to the construction site where they are interconnected together using cold construction joints and/or prestressing system.
While some have attempted to solve the above problems using Ultra-high-performance concrete (UHPC) or Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC), for the complete beams, these have been found to have their own issues, particularly with problems of quality control and exceptional high cost. More specifically as provided in “EVALUATION OF ULTRA-HIGH-PERFORMANCE FIBER-REINFORCED CONCRETE”by Celik Ozyildirim, Ph.D., P.E. of the Virginia Center for Transportation Innovation & Research, August 2011, “VDO's Structure and Bridge Division should not use UHPC because of its high cost” and further specifies that UHPC is not practical for use in bridges. Therefore, while UHPC has positive performance characteristics, the problems with quality control and high cost have prevented its adaption as a bridge material in the industry. As further provided in Nebraska Department of Roads Project Number: P310 “APPLICATION OF ULTRA-HIGH PERFORMANCE CONCRETE TO BRIDGE GIRDERS” by Maher K. Tadros and George Morcous, February 2009, commercial UHPC mixes cost ten times conventional mixes, and need special mixing and curing procedures that are not convenient to precasters, all of which “represent serious obstacle towards its wide use in practical and economical bridge applications”. Therefore, there is a need for the performance of UHPC, without the associated costs of UHPC, as well as a way to minimize the difficulty of pouring a beam having expected performance characteristics.